The invention relates to a press for cold forming of workpieces from a metal sheet having a base frame, at least one C-frame, an upper and a lower tool, whereby one of the upper tool and the lower tool is connected with a piston actuated by pressure means or by an eccenter disc.
In different working processes, especially in sheet metal machining, presses of different forms are used, the frames of which are carried out according to the magnitude of the forces occurring during the working process. The versatility of the presses is enhanced when the height of the interior working space is bigger and when the stroke is accordingly higher because, in such a case, high tools and high drawing devices can be mounted in the press. The presses for cold forming of workpieces having C-frames have an advantage of being accessible on three sides as against the frames having two columns which are accessible on two sides only.
A disadvantage of the presses having C-frames consists in that they are elastic because of the forces occurring during the working process. The elastic movement of the C-frame takes place both in the vertical axis and in the horizontal axis of the press. The most important elastic movement is, however, that one caused by the swinging motion of the upper arm of the C-frame in a vertical axis lying perpendicularly to the plane passing through the upper and the lower arms of the C-frame. Owing to this swinging motion, the upper tool attached to the upper arm of the C-frame is displaced in respect to the lower tool, resulting in faulty products, which is comprehensible. The number of the elastic movements is 100 kg/.mu. in average with presses of 60 - 100 t of nominal capacity. Small presses have a smaller number and big presses have a higher number of elastic movements. Owing to this elastic movement, the tools are worn off quicker and the stability of their cutting edges gets worse. The working life of such a tool is accordingly shorter.
In order to withstand the forces occurring during the working process, the C-frames have to be built rigidly, by such a rigid construction the elastic movements of the C-frame should be eliminated as far as possible.